Heated substrate doping is a focus of doping process development for advanced large scale integration (LSI) fabrication. An example is ion implantation on heated substrates. While thermal management of beam implant doping profiles is becoming well established, the absence of a clear mechanism for surface reactions and solid state chemistry for thermal assisted plasma processing (radical assisted plasma doping, atomic layer deposition (ALD) and atomic layer etching (ALE)) has hindered its adoption.
Advances in metrology and computational methods have recently provided more insight into how solid state surface chemistry can be controlled. Plasma doping technology is successful because of how additives, dopants and ions can be controlled. In the ALD, a means of predicting dopant incorporation and film properties such as damage density would allow the development of methods for their construction.
Doping is conventionally performed by substrate damage assisted and materially benign processes. Damage assisted includes ion implantation where very high energy ions are thrown at a surface either by a beam or through the assistance of a plasma source in contact with the substrate. Laser methods are also used to melt the surface and mix dopants and substrates. Benign methods include solid state doping, liquid phase doping that in effect involve the deposition of a film that is infused using heat or another form of energy. Plasma doping is a non-damaging hybrid whereby radical dopants are infused aided by conventionally low energy ions and film formation. Electrical activation in all methods includes a form of annealing with thermal energy.
Silicon doping of fins, for example, benefits perfectly from plasma doping (excluding plasma source ion implantation (PIII) technology) in that shallow high dose damage free dose is possible. Germanium and Group III-V implant requirements are that both deep (not shallow) high dose (dopant) profiles can be imparted into a substrate with an abrupt transition. There is a need for concurrent control of both plasma-surface interactions and the thermal materials chemistry of the surface and near surface of the substrate. For example, Group III-V material implant is but one example of a materials system that would benefit from concurrent control of variables mentioned above. In addition to electrical activation (doping), surface and near surface chemistry control is needed for precise nano-layer deposition and nano-scale etch processes. Furthermore, there is a need for processes that can meet doping objectives including damage density, amorphization depth, and transition abruptness of the doping profile.